Vehicle retraints have been employed to lock a truck or other vehicle to a loading dock to prevent the truck from accidentally pulling away from the dock during a loading operation. A conventional loading dock includes a doorway which is normally enclosed by an overhead door. When the truck backs toward the loading dock for the loading operation, the rear end of the truck body completely encloses the doorway so there is no direct communication between the truck driver and an operator on the loading dock. As the loading operation is normally carried out by a fork lift truck moving between the dock and the truck bed, it is critical that the truck not move away from the loading dock during the loading operation. Thus, truck restraints have been employed to prevent the accidental movement of the truck from the dock during a loading operation.
The conventional truck restraint is mounted on the front face of the dock and is operable to engage the ICC bar at the rear end of the truck. The ICC bar is a horizontal bar or beam located beneath the truck bed to prevent underriding of an automobile in the event of a rear end collision.
A common form of truck restraint as disclosed in U.S. Pat. No. 4,488,325 include a power operated hook, in which the hook is moved verticlaly from a lower storage position to an upper operating position where it engages the ICC bar. Other truck restraints, such as disclosed in U.S. Pat. Nos. 4,282,621 and 4,264,259 employ a pivoting hook in which the hook is pivoted either manually or through a power operated mechanism from a lower inopertive position to an upper operative or lock position.
It is also known in the prior art to utilize a sliding carriage plate in a vehicle restraint to permit the restraint to follow upward and downward movement of the truck bed when the vehicle restraint is in the locked position. As disclosed in U.S. Pat. Nos. 4,282,621 and 4,264,259, a generally triangular carriage plate is mounted for sliding movement on the front face of the dock and the forward edge of the plate slopes downwardly and outwardly away from the dock. The carriage plate, as disclosed in the aforementioned patents, is biased to an upper position, and as the truck backs toward the loading dock, the ICC bar will engage the inclined surface wedging the plate downwardly against the force of the biasing means. With the truck engaged with the bumpers on the dock face, a hook is then moved upwardly to engage the ICC bar and lock the truck to the dock.